Flights to Heathrow Airport were delayed by up to three hours after a "technical issue" affected lighting on the runways.

Flights have since been landing at the airport this morning.

In an email to CNBC, the airport clarified: "Both arrivals and departures will be impacted this morning (hour of darkness when lights are required)".

The worst delay was to a United Airlines flight from Newark, near NY, which was operating three hours and five minutes behind schedule.

British Airways said early Wednesday morning United Kingdom time that it was delaying flights that had already departed and would start "diverting some flights that are airborne and due to arrive at Heathrow shortly".

It added it would start "diverting some flights that are airborne and due to arrive at Heathrow shortly". The problem was resolved by 6.05am, but the airport - the busiest in Europe - said that customers should check their airline flight status before travelling.

However, many passengers expressed their frustration and anger on social media.

A spokeswoman for British Airways said: "There was an issue with Heathrow Airport's airfield lighting during the night".

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